In recent years, a requirement for a reduction of fuel consumption of a tire has been getting higher and the reduction of fuel consumption is also required to an inner liner which is arranged inside a tire and has a function of decreasing the amount of air leaked to the outside from the inside of a pneumatic tire and improving air permeation resistance.
Traditionally, a rubber composition for an inner liner has improved its air permeation resistance by using a rubber composition comprising a rubber component mainly composed of a butyl-based rubber. However, the rubber composition comprising a large amount of a butyl-based rubber has a problem of lowered fuel efficiency and lowered adhesive property to other components.
In JP 2011-057788 A, a technique of making a thickness of an inner liner thinner by using an inner liner using a polymer composition mainly composed of a polymer mixture comprising a thermoplastic resin which has better air permeation resistance than that of a butyl-based rubber, and thereby attempting improvement of fuel efficiency by weight saving of a tire. However, since the inner liner mainly composed of a resin generally has a small elongation at break and the physical properties thereof are widely different from those of other tire components which are mainly composed of a rubber component, there is a problem of deteriorated processability and adhesive property to adjacent components and there is also a problem in flexing crack growth resistance.
In JP 2006-249147 A and JP 2008-297462 A, an environment-friendly inner liner which has improved processability and flexing crack growth resistance by using a rubber composition mainly composed of a natural rubber for an inner liner to decrease a used amount of oil resources is described but there is room for improvement with respect to fuel efficiency.